Highly Efficient Multiple Watt Gain-Switched 1.7 μm All-Fiber Laser Pumped by 1.6 μm Harmonic Dissipative Soliton Resonance Pulses

Here, we firstly utilize a newly explored 1.6 μm harmonic dissipative soliton resonance (DSR) pulses as a pump source to realize a highly efficient gain-switched thulium fiber laser at 1719.52 nm. The 1.6 μm DSR pulses with a fundamental repetition rate of 360 kHz were produced from a nonlinear amplifying loop mirror (NALM) ring cavity, which directly output high power mode-locking pulses due to freedom of soliton-area limitation and pulse breaking. The harmonic mode-locking (HML) operation was achieved by properly adjusting the polarization controllers (PCs). The thulium fiber laser cavity constructed by a Fiber Bragg Grating (FBG) pair was resonantly (in-band) pumped by the 1.6 μm harmonic DSR pulses. Taking the merit of the strong absorption of Tm 3+ at 1.6 μm and the laser cavity having a low insert loss, the 1.7 μm gain-switched fiber laser with the maximum repetition rate of 2.16 MHz, corresponding to the average power of 2.826 W and the pulse energy of 1.33 μJ, was obtained at a high slope efficiency of about 71.9%. The maximum output power could exceed 3 W with a high slope efficiency of over 70%, which is the record in 1.7 μm all-fiber pulsed thulium lasers.